JP2768886B2 - Level control device for mold level in continuous casting machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for maintaining and controlling a metal level in a mold of a continuous casting machine to a target metal level with high accuracy.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 7, there is known a mold level control device in a continuous casting machine which maintains a mold level in a mold at a target level. ing.

FIG. 7 is a view showing the construction of a conventional continuous casting machine equipped with a conventional mold level control device in a mold. In FIG. 7, reference numeral 51 denotes a molten steel pot, and a tundish installed below the molten steel pot 51. A bottom plate 53 having a through hole 53a having the same diameter as the molten steel outflow hole 52c of the tundish 52 is fixed to the lower surface of the tundish 52. A seal plate 54 having a through-hole 54a having the same diameter as the molten steel outflow hole 52c is provided at a position below the plate 53 at a predetermined interval, and a tundish 52 is provided between the plates 53, 54. Is provided with a slide valve 55 provided with a through hole 55a having the same diameter as the molten steel outflow hole 52c.

[0004] The slide valve 55 is a tundish 5
This is for adjusting the amount of molten steel that is injected into the mold 56 from the mold 2 and becomes the cast slab 57. The molten metal level in the mold 56 is maintained at a target molten metal level by a molten metal level control device in a mold described later. By sliding the position of the through hole 55a with respect to the through holes 53a and 54a of the other plates 53 and 54, the opening degree of the through hole 55a is corrected and adjusted.

The structure of a conventional mold level control device in a mold will be described. An upper bracket 52a is fixed to a side surface of a tundish 52, and the upper bracket 52a
, A hydraulic cylinder 61 is swingably mounted.
A lower bracket 52b is fixed to a side surface of the tundish 52 below the upper bracket 52a, and a link 62 is swingably attached to the lower bracket 52b. The tip of the piston rod 61a is connected with a pin. Further, the other end of the link 62 is connected to the slide valve 55 via a connecting rod 63.

Reference numeral 64 denotes a differential transformer for detecting the position of the piston rod 61a of the hydraulic cylinder 61, the main body of which is fixed to the hydraulic cylinder 61 and the like by a support member (not shown), and the rod-shaped core of which is a piston rod. It is moved together with 61a, and outputs a voltage signal according to the position of the piston rod 61a.

[0007] Further, reference numeral 65 denotes a level meter of an eddy current type, an electrode following type or the like for detecting the level of the molten metal in the mold 56, 65a denotes an amplifier of the level gauge 65, and 66 denotes a target for setting the level of the molten metal. The target level setting device 67 receives the output of the level meter 65 and the output of the target level setting device 66 via the amplifier 65a as inputs, and calculates the difference between them as PID.
A valve opening command section 68, which is operated by an arithmetic circuit or the like and outputs an operation command value corresponding to the difference between the two outputs, is a cylinder control section 68 comprising a normal directional control valve, a servo amplifier and the like. The unit 68 includes a valve opening command unit 6
7 (operation command value) and the output of the differential transformer 64 used for positioning control, and the level of the molten metal in the mold 56 is set in accordance with the output of the valve opening instruction section 67. This is for controlling the operation of the hydraulic cylinder 61 so that the hydraulic cylinder 61 is held.

Next, the operation of the conventional mold level control device in the mold constructed as described above will be described. The amount of molten steel injected into the mold 56 through the slide valve 55 and the amount of withdrawal of the slab 57 are unbalanced. Occurs, and the level total 6
5 and the output of the target level setting unit 66, an output corresponding to the difference between the two outputs is given from the valve opening command unit 67 to the cylinder control unit 68.

The cylinder controller 68 operates the hydraulic cylinder 61 accordingly. For example, when the molten metal level in the mold 56 is higher than the target molten metal level, the piston rod 61a of the hydraulic cylinder 61 is extended, and the slide valve 55 is slid via the link 62 and the connecting rod 63 so that the opening degree is increased. Is adjusted to reduce the amount of molten steel injected into the mold 56.

[0010]

However, the above-described conventional mold level control apparatus in a mold is useful for maintaining and controlling the mold level in the mold to a target mold level. As described above, there is a problem in the control accuracy of the level of the molten metal.

That is, since the hydraulic cylinder 61 is operated and the slide valve 55 is slid through the connecting portion such as the link 62 or the connecting rod 63 to correct the opening thereof, the position of the connecting portion is not present. Due to the play of the mechanical system due to the gap, the amount of expansion and contraction of the piston rod 61a of the hydraulic cylinder 61 and the amount of sliding of the slide valve 55 are shifted,
Precise level control cannot be performed.

In particular, when the sliding direction of the slide valve 55, which is important for controlling the level of the molten metal, is changed, that is, when the operating direction of the hydraulic cylinder 61 is changed, the play of the connecting portion causes a control delay. As a result, the level of the molten metal level becomes large, and as a result, the quality of the cast piece 57 is reduced.

It should be noted that the value of the play of the connecting portion fluctuates from the value before the start of casting due to the high temperature atmosphere during casting, and the slide valve 55, the link 62, the connecting rod 63, etc. The value is different each time it is exchanged, so that it is difficult to grasp the value as a constant value in advance.

Therefore, it is conceivable to automatically calculate and compensate the above-mentioned mechanical play value on-line automatically. At this time, if a control system parameter such as a change in flow characteristic changes, an optimum play compensation value is calculated. There was also a problem that it became difficult to do so.

The present invention is intended to solve such a problem, and incorporates mechanical play in a control system collectively in an on-line manner so that the mechanical play can be automatically performed without changing the control system parameters. It is an object of the present invention to provide a mold level control device in a continuous casting machine capable of maintaining the mold level in a mold in an optimum state with high accuracy over the entire length of a casting.

[0016]

In order to achieve the above-mentioned object, in the continuous casting machine according to the present invention, an apparatus for controlling a level of a molten metal in a mold comprises an opening of a slide valve for adjusting an amount of molten steel injected into a mold from a tundish. A hydraulic cylinder that adjusts the piston rod by expanding and contracting a piston rod, a position detector that detects the position of the piston rod, a level meter that detects the level of the level in the mold, a detection result of the level meter, and a target level. A valve opening command section that calculates a deviation from the level and outputs an operation command value corresponding to the deviation, and operates the hydraulic cylinder in accordance with the output of the valve opening command section to thereby operate the hydraulic cylinder. In the apparatus for maintaining and controlling the molten metal level at the target molten metal level, a direction in which the hydraulic cylinder is operated is determined based on an output of the valve opening command unit, and an operating direction is determined. Backlash correction control means for adding a predetermined play correction value to the output of the valve opening command section when the output is changed, and when the output from the valve opening command section is held at a constant value for the longest time Wherein the mechanical backlash existing between the slide valve and the piston rod is calculated as the predetermined backlash correction value, and the backlash correction value calculating means is output to the backlash correction control means. .

[0017]

In the above-described apparatus for controlling the level of the level in the mold in the continuous casting machine of the present invention, when the control is in a good state regardless of the change of the control system, in other words, when the backlash correction value is optimal,
The optimal play correction value is calculated by paying attention to the operation time of the hydraulic cylinder, that is, the time during which the output value of the valve opening command section does not change becomes longer.

That is, the backlash correction value calculating means calculates the mechanical play between the slide valve and the piston rod, and the output from the valve opening command section is maintained at a constant value for the longest time. The mechanical play at the time of the movement is calculated as a predetermined play correction value.

In the backlash correction control means, the direction in which the hydraulic cylinder is operated is determined based on the output of the valve opening command section, and the output of the valve opening command section when the operating direction changes is changed to the backlash correction section. By adding the backlash correction value from the value calculation means, mechanical backlash is integrated into the control system collectively online, and the backlash is automatically corrected without any change in the control system, and the hydraulic cylinder The opening degree of the slide valve can be accurately and accurately corrected by the expansion and contraction operation of the piston rod.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a continuous casting machine provided with a mold level control device according to an embodiment of the present invention. In 1, the continuous casting machine has the same configuration as that described in FIG. 7, 1 is a molten steel pot, 2 is a tundish, 3 is a bottom plate, 4 is a seal plate, and 5 is a mold level control device in a mold described later. The slide valve whose opening degree of the through hole 5a is adjusted by the control means, 6 is a mold, and 7 is a cast piece. The plates 3 and 4 sandwiching the slide valve 5 are also provided with through holes 3 having the same diameter as the through holes 5a.
a and 4a are formed respectively, and the tundish 2
Of the molten steel outflow hole 2c.

As shown in FIG. 1, as a configuration of the mold level control device in the mold, an upper bracket 2a is fixed to a side surface of the tundish 2, and the upper bracket 2a
, A hydraulic cylinder 8 is swingably mounted. A lower bracket 2b is fixed to a side surface of the tundish 2 below the upper bracket 2a, and a link 9 is swingably attached to the lower bracket 2b. The tip of the rod 8a is connected with a pin. Further, the other end of the link 9 is connected to the slide valve 5 via a connecting rod 10.

Reference numeral 11 denotes a differential transformer for detecting the position (displacement) of the piston rod 8a of the hydraulic cylinder 8.
(Position Detector), the main body is fixed to the hydraulic cylinder 8 and the like by a support member (not shown), and the rod-shaped core is moved together with the piston rod 8a.
A voltage signal is output according to the position of a. 12
Is a level meter for detecting the level of the molten metal in the mold 6, and 12a is an amplifier of the level meter 12.

Reference numeral 13 denotes a level meter 12 via an amplifier 12a.
A moving average processing unit for performing a moving average process on the output (level detection result) to remove a secondary vibration component included in the level detection result and outputting an actual level fluctuation component; A target level setting unit 15 for setting is used to calculate a deviation between the output of the level meter 12 and the output of the target level setting unit 14 input via the amplifier 12a and the moving average processing unit 13 by a PID operation circuit or the like. And outputs a value MV corresponding to the difference between the two outputs.

Reference numeral 16 denotes a backlash correction control unit for outputting a valve opening correction signal in accordance with a procedure described later with reference to FIG. 6. The backlash correction control unit 16 determines the direction in which the hydraulic cylinder 8 is operated by the valve opening command unit 15. a cylinder actuating direction determining unit 16a that determines on the basis of the output MV of backlash correction value G _n to be described later to output MV of the valve opening command unit 15 when determining the change in the operating direction by the cylinder operating direction judgment part 16a And an adder 16b that adds

Reference numeral 17 denotes an online play correction value calculation section for calculating and outputting a play correction value G _n to the play correction control section 16. The play correction value calculation section 17 is provided between the slide valve 5 and the piston rod 8. Is calculated, and the mechanical play at the time when the output MV from the valve opening command unit 15 is maintained at a constant value for the longest time is calculated as a predetermined play correction value _Gn . Things. A detailed calculation procedure in the backlash correction value calculation unit 17 will be described later with reference to FIG.

Reference numeral 19 denotes the moving average processing unit 1 described above.
3, target level setting unit 14, valve opening command unit 1
5, a level controller comprising a backlash correction controller 16 and a backlash correction value calculator 17;
The cylinder controller 23 includes a servo valve 21 and a hydraulic unit 22. The cylinder controller 23 receives an output of the level controller 19 and an output of the differential transformer 11 used for positioning control as inputs, Output of controller 19 (valve opening correction signal after backlash correction)
In order to control the operation of the hydraulic cylinder 8 so that the level of the molten metal in the mold 6 is maintained at the target level.

Next, the operation of the apparatus for controlling the level of the molten metal in the mold according to the present embodiment constructed as described above will be described. In this embodiment, when the backlash correction value _Gn is insufficient, the waveform of the output MV of the valve opening command unit 15 is as shown in FIG. 3, and when the backlash correction value _Gn is excessive, the valve While the waveform of the output MV of the opening degree command unit 15 becomes as shown in FIG. 4, when the control is in a good state regardless of the change of the control system, that is, when the backlash correction value _Gn is optimal, The optimal play correction value _Gn is calculated by paying attention to the fact that the operation amount of the cylinder 8, that is, the output MV of the valve opening command section 15 is kept at a constant value for a long time.

Therefore, the backlash correction value calculation unit 17 of the present embodiment
, The backlash correction value _Gn is calculated according to the flowchart shown in FIG. In the description of the flowchart, A1 to A7 indicate processing procedure (step) numbers.

When the control is started, the backlash correction value calculation section 1
7, the molten metal level PV obtained by the level meter 12 at each predetermined sampling interval Δt and the valve opening command unit 1
5 and the operation command value MV from the
Based on the data such as V, the mechanical backlash existing between the slide valve 5 and the piston rod 8 is calculated (step A1), the current output MV from the valve opening command unit 15 is set to MV2 and the previous output is set. MV2 is set to MV1
(Step A2).

Thereafter, the previous output MV1 and the current output MV2
Is determined (step A3), and if not, the timer time (not shown) is reset (step A7), while if they are equal, the timer time T
Is counted up (step A4), and the time T during which the output MV of the valve opening command section 15 has not changed is compared with the maximum time TMAX up to the previous time (step A5).

As a result of the comparison, when the timer time T of the timer is larger, the current timer time T is replaced with TMAX, and the mechanical play at that time is output and stored as the optimal play correction value _Gn (step A6).

As described above, the backlash correction value _Gn calculated by the backlash correction value calculation unit 17 in accordance with the flowchart shown in FIG. 2 is output to the addition unit 16b of the backlash correction control unit 16, and the backlash correction control unit 16 In, the correction control is executed according to the flowchart shown in FIG. In addition,
In the description of the flowchart, B1 to B4 indicate processing procedure (step) numbers.

First, when the control is started, the output change amount ΔMV _n (having a positive or negative sign depending on the direction) from the valve opening command section 15 is read at every predetermined sampling interval (step B1). Then, a currently read output variation .DELTA.MV _n, the sign of the product of the previous change amount .DELTA.MV _n-1, to determine the direction of operating time of the hydraulic cylinder 8 (step B2), the hydraulic cylinder 8 and the previous when actuating the same direction _{(ΔMV n · ΔMV n -1 ≧} 0) , the current output M
The V _n as it is output to the cylinder control unit 23 as a valve opening correction signal (step B3), the flow returns to step B1.

[0034] In contrast, when the actuating a hydraulic cylinder 8 to the previous and reverse direction is determined _{(ΔMV n · ΔMV n-1} <0) in step B2, the input from the backlash correction value calculation unit 17 Of the current play correction value G _n and the output M
And a V _n are added by the addition unit 16b, and outputs the addition result to the cylinder control unit 23 as a valve opening correction signal
(Step B4), and the process returns to Step B1.

The operation direction of the hydraulic cylinder 8 is determined by the cylinder operation direction determination unit 16a based on the positive / negative determination of ΔMV _n and ΔMV _n-1 described above.

In the cylinder controller 23, the servo amplifier 20 opens and closes the servo valve 21 based on the valve opening correction signal from the level controller 19 and the position information of the piston rod 8a from the differential transformer 11. The operation of the hydraulic cylinder 8 is controlled so that the position of the piston rod 8a becomes a valve opening correction signal, that is, the slide valve 5 has an appropriate opening.

As described above, according to the mold level control device in the mold of the present embodiment, the mechanical play present between the slide valve 5 and the piston rod 7 is calculated in the play correction value calculating unit 17 and the valve is operated. calculates the mechanical backlash when held at a constant value output MV opening command unit 15 over the longest as backlash correction value G _n, outputs the backlash correction value G _n to play correction control unit 16 However, when the operating direction of the hydraulic cylinder 8 changes, the hydraulic cylinder 8 is additionally operated by the predetermined play correction value _Gn, so that the play is automatically corrected and the piston rod of the hydraulic cylinder 8 is 8
The opening degree of the slide valve 5 is reliably and accurately corrected by the expansion and contraction operation a.

As a result, the mechanical play can be integrated into the control system at a time online, and the mechanical play can be automatically corrected without changing the control system parameters.
It is possible to maintain the level of the inner metal level at the target level with high accuracy and stably over the entire length of the casting.

In the above embodiment, the differential transformer 11 is used to detect the position (displacement) of the piston rod 8a of the hydraulic cylinder 8, but a potentiometer or the like may be used as the position detector.

The apparatus for controlling the level of the molten metal in the mold according to the present invention has a structure in which the hydraulic cylinder 8 is arranged on the bottom side of the tundish 2 or the level of the molten metal in the mold is actuated by operating the hydraulic cylinder. Naturally, the present invention can also be applied to a configuration in which the opening degree is adjusted by the opening operation, and the same operation and effect as those of the above embodiment can be obtained.

[0041]

As described above in detail, according to the apparatus for controlling the level of the level in the mold in the continuous casting machine of the present invention, the direction in which the hydraulic cylinder is operated is determined based on the output of the valve opening command section, and the operation is determined. A backlash correction control means for adding a predetermined backlash correction value to the output of the valve opening command section when the direction changes, and a slide valve when the output from the valve opening command section is held at a constant value for the longest time And a mechanical correction value calculating means for calculating a mechanical play between the piston rods as a predetermined play correction value and outputting it to the play correction control means. And the mechanical play can be automatically corrected without any change in the control system, and the level of the molten metal in the mold can be accurately and stably maintained at the target level over the entire length of the casting. There can be effectively.

[Brief description of the drawings]

FIG. 1 is a control block diagram showing a mold level control device in a mold in a continuous casting machine as one embodiment of the present invention.

FIG. 2 is a flowchart illustrating a procedure of calculating a play correction value by a play correction value calculating unit according to the present embodiment.

FIG. 3 is a graph showing an output waveform of a valve opening command unit when a play correction value is insufficient.

FIG. 4 is a graph showing an output waveform of a valve opening command unit when the backlash correction value is excessive.

FIG. 5 is a graph showing an output waveform of a valve opening command unit in a case where a backlash correction value is optimal.

FIG. 6 is a flowchart illustrating an example of a control procedure performed by the play correction control unit according to the embodiment.

FIG. 7 is a configuration diagram showing a conventional continuous casting machine provided with a mold level control device in a mold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molten steel pot 2 Tundish 2a Upper bracket 2b Lower bracket 2c Molten steel outflow hole 3 Bottom plate 3a Through hole 4 Seal plate 4a Through hole 5 Slide valve 5a Through hole 6 Mold 7 Cast piece 8 Hydraulic cylinder 8a Piston rod 9 Link 10 Connecting rod DESCRIPTION OF SYMBOLS 11 Differential transformer 12 Level meter 12a Amplifier 13 Moving average processing part 14 Target molten metal level setter 15 Valve opening command part 16 Playback correction control part 16a Cylinder operation direction judgment part 16b Addition part 17 Online play correction value calculation part 18 Initial Value setter 19 Level controller 20 Servo amplifier 21 Servo valve 22 Hydraulic unit 23 Cylinder controller

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-251645 (JP, A) JP-A-3-77757 (JP, A) (58) Fields investigated (Int.Cl. ⁶ , DB name) B22D 11/00-11/22

Claims (1)

(57) [Claims] A hydraulic cylinder for adjusting an opening degree of a slide valve for adjusting an amount of molten steel injected from a tundish into a mold by expanding and contracting a piston rod; a position detector for detecting a position of the piston rod; A level meter for detecting the level of the molten metal in the mold, and a valve opening command section for calculating a deviation between the detection result of the level meter and the target level of the molten metal and outputting an operation command value according to the deviation; In the mold level control device in a continuous casting machine for maintaining and controlling the mold level in the mold at the target mold level by operating the hydraulic cylinder in accordance with the output of the valve opening command section, The direction in which the hydraulic cylinder is operated is determined based on the output of the valve opening command section, and a predetermined play is added to the output of the valve opening command section when changing the operating direction. Backlash correction control means for adding a value, and mechanical backlash existing between the slide valve and the piston rod when the output from the valve opening command unit is kept at a constant value for the longest time. And a backlash correction value calculating means for calculating the predetermined backlash correction value and outputting the result to the backlash correction control means.